An iPhone Fell 16,000 Feet. Its Screen Didn’t Break. How?
Reading Time: 5 minutesHow Can a Phone Survive a Fall From a Plane Without Cracking? Let’s Look at the Physics., Part of the answer is that phone screens have gotten more durable. And part of it is basic physics., An iPhone fell out of the Alaska Airlines plane and didn’t crack.
Last week’s Alaska Airlines incident—when a sheet-metal door plug fell off a Boeing 737 Max 9 plane at around 16,000 feet—was a scary reminder that small errors can have massive consequences. But the event also featured some small miracles. For instance, no one was sitting in the window seat where the door blew out, according to a passenger on the flight. Then there was the iPhone discovered on the side of a road in Portland, Oregon, with an unlocked phone screen open to an Alaska Airlines baggage claim email: Not only had the phone survived the fall, but it didn’t have a single scratch.
The phone’s discovery went viral on X, formerly known as Twitter. It was actually one of two phones to be found from the 737 incident—and both were still in working condition, confirmed the National Transportation Safety Board to MediaDownloader via email. The devices join a growing club of phones that have reportedly survived falls from planes, including one that fell from 1,000 feet in 2018 and another, from 9,300 feet, in 2015. (In these instances, there was no disaster—the planes were small enough that the phones were accidentally dropped out of them.)
The resilience of these phones can partly be attributed to the fact that smartphone screens have steadily improved over the years, says Collin Wilkinson, the director of the Center for Glass Innovation at Alfred University. Yet, phones do still break falling from clumsy hands and kitchen tables. How can a phone survive a 16,000-feet skydive but not a short tumble to the floor? What factors determine whether it will crack?
First, there’s the height of the fall itself. The main difference between a phone falling from the sky vs. from someone’s hand is the speed at which the phone hits the ground, because objects accelerate as they fall. A higher fall means more time to speed up—to a point. Physicist Rhett Allain graciously worked out the numbers for me: A phone falling from 4 feet would be traveling at about 10 mph right when it hit the ground, while a phone falling from 16,000 feet would be traveling at around 60 mph.
After a certain number of feet, it doesn’t actually matter how high the phone is, because at some point in its journey to the ground it will stop speeding up. When air resistance (which pushes the object in the opposite direction of its motion, thus upward for a falling object) reaches the same magnitude as the earth’s gravitational force (which pulls the object down), the object stops accelerating and falls at a constant speed, something called terminal velocity. At what point does a phone hit terminal velocity? Allain calculated this for me too: An iPhone 11 will stop speeding up after about 328 feet. So that impressive 16,000 feet isn’t practically any different from dropping a phone from about 328 feet (a height in the ballpark of a 30-story building—still high!).
But all of that height stuff, while interesting, doesn’t actually matter much to the phone’s likelihood of survival. After all, ‘it’s not the falling that kills you,’ says Allain, who teaches physics at Southeastern Louisiana University and previously served as a consultant for MythBusters. ‘It’s the stopping that kills you.’
Whether a phone’s screen breaks is determined by the end of the fall—specifically, what the phone lands on, and the way it lands. Physicswise, the landing material is important because it changes how long the impact lasts. ‘The longer it takes for the impact to occur, the smaller the force,’ says Allain. If you drop your phone on a pillow, the pillow will compress beneath the phone, which lengthens the impact time. If you drop it on concrete, there’s no give; the impact will be very short, since the phone slows down basically all at once, and thus the force will be very large. In this case, the phone was discovered in an area with lots of big bushes, which is a great thing to land in. ‘Every time it contacts different parts of the bush, it’s slowing down a little bit,’ Allain says. ‘The impact time will be larger than it would be if you dropped your phone on the kitchen floor.’
In addition to where the phone lands, it matters how it lands. ‘If you truly have a piece of glass that falls flat and lands perfectly even, it should not break, no matter what,’ Wilkinson says. That’s because the force of the fall is spread out across the glass. But if the screen lands at an angle, or if it hits a pebble, a lot of pressure is exerted on a very small point. In glass, there are little flaws, and ‘those flaws are the points where cracks can start,’ Wilkinson says. Research into strengthening glass involves figuring out how to manage those flaws, given their existence.
And that’s where recent glass innovations have made a big difference. Many smartphone manufacturers, including Samsung, Sony, and Google, opt to use the popular Gorilla Glass made by Corning Incorporated. That glass relies on a ‘really clever trick’ called ion exchange, says Wilkinson. The glass is placed in a molten potassium bath, where the small silica atoms present in the glass’s molecular structure switch places with the larger potassium ions in the bath. The potassium ions are physically bigger, and better fill up the space, thus making the glass stronger.
The past few generations of Apple iPhones, starting with the iPhone 12, have used a different technology, called Ceramic Shield, also created by Corning. Apple has claimed (and some reviews have anecdotally borne out) that this kind of screen is more durable than previous iPhone screens. While the exact science is proprietary, Wilkinson thinks Corning likely grows tiny crystals, then creates the glass around the crystals, something called a glass-ceramic. If a crack does happen, it will run into a crystal, making it unable to propagate in a straight line and less likely to shatter the whole screen. The iPhone that was found on the side of the road appeared to be a relatively new model (there was no home button), so the screen would have benefited from whatever new and improved glass-strengthening techniques Apple was using.
Even among manufacturers that use the same techniques, the exact recipes and process of strengthening the glass, plus the thickness of the screen, are tweaked by each company, which explains why some phones are more resilient than others. In 2018 Tom’s Guide dropped smartphones from 4, 6, and 100 feet and found that the toughest phone overall was the Motorola Moto Z2 Force, followed by the LG X Venture and the iPhone X.
‘I remember the first iPhone, and I remember people breaking it like crazy,’ Wilkinson says. ‘The fact that we’re now at a point where they rarely break from that is really a testament to the amount of progress that the glass has made.’
So, given the right set of circumstances, the possibility that a phone could survive a skydive is not so wild. Indeed, the phone’s durability was not the most amazing part of the story to Allain. ‘The amazing thing,’ he says, ‘is that it was unlocked.’
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